1. Field of the Invention
The present invention relates to a pixel structure and a repairing method thereof, and particularly to a pixel structure and a repairing method thereof by which slight bright dots can be avoided.
2. Description of Related Art
Cathode Ray Tube (CRT) displays have long dominated the display market, although having the disadvantages of bulkiness, radiation contamination, and energy consumption and not being able to satisfy the demands of the consumers for a slimmer display consuming less power. Therefore, Thin Film Transistor-Liquid Crystal Displays (TFT-LCD), having the advantages of higher image quality, better space efficiency, lower power consumption, and zero radiation, have gradually become a mainstream product of the display market.
A TFT-LCD mainly comprises a TFT array substrate, a color filter array substrate and liquid crystal layers, wherein the TFT array substrate comprises a plurality of pixel structures arranged in an array, each pixel structure comprises a TFT, a pixel electrode and a storage capacitor. Such a pixel structure may become a dot defect when an abnormal leakage of the storage capacitor occurs due to particles or broken dielectric layers of the storage capacitor. Some laser repairing technologies have been developed for repairing such dot defects, such as the disclosure in TW Patent Application No. 516225.
FIG. 1 is a schematic diagram for illustrating a feed through voltage (Vft) respectively of a normal pixel structure and an abnormal pixel structure. Referring to FIG. 1, the feed through voltage Vft=Cgd·(Vgh−Vgl)/(Cst+CLC+Cgd), wherein the Cgd is the parasitic capacitance of the gate electrode and the drain electrode of a TFT; Vgh is the threathold voltage of the gate electrode; Vgl is the turning-off voltage of the gate electrode; Cst is the storage capacitance of the pixel structure; and CLC is the liquid crystal capacitance. It can be known from the above equation that the value of the feed through voltages will become larger or smaller when the storage capacitance in a repaired pixel structure becomes smaller or larger. Note that although most conventional laser repairing technologies can be used for repairing abnormal pixel structures, the storage capacitances Cst of the repaired pixel structures are often different from the storage capacitances of the normal pixel structures. Therefore, there will be differences between the feed through voltages of the repaired pixel structures and the normal pixel structures, such that the repaired pixel structures become slight bright dots.